Increasing Capacity in Wireless Communications

ABSTRACT

Techniques to increase the capacity of a W-CDMA wireless communications system. In an exemplary embodiment, early termination ( 400 ) of one or more transport channels on a W-CDMA wireless communications link is provided. In particular, early decoding ( 421, 423 ) is performed on slots as they are received over the air, and techniques are described for signaling ( 431, 432 ) acknowledgment messages (ACK&#39;s) for one or more transport channels correctly decoded to terminate the transmission of those transport channels. The techniques may be applied to the transmission of voice signals using the adaptive multi-rate (AMR) codec. Further exemplary embodiments describe aspects to reduce the transmission power and rate of power control commands sent over the air, as well as aspects for applying tail-biting convolutional codes ( 1015 ) in the system.

RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 12/424,050,entitled “Increasing Capacity in Wireless Communications,” filed Apr.15, 2009, which claims priority to U.S. Provisional Application Ser. No.61/060,119, entitled “Apparatus and Methods for Increasing Capacity inWireless Communications,” filed Jun. 9, 2008, and U.S. ProvisionalApplication Ser. No. 61/060,408, entitled “Apparatus and Methods forIncreasing Capacity in Wireless Communications,” filed Jun. 10, 2008,and U.S. Provisional Application Ser. No. 61/061,546, entitled“Apparatus and Methods for Increasing Capacity in WirelessCommunications,” filed Jun. 13, 2008, the contents of which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates generally to digital communications, andmore specifically, to techniques for reducing transmission power andimproving the capacity of wireless digital communications systems.

BACKGROUND

Wireless communications systems are widely deployed to provide varioustypes of communication such as voice, packet data, and so on. Thesesystems may be based on code division multiple access (CDMA), timedivision multiple access (TDMA), frequency division multiple access(FDMA), or other multiple access techniques. For example, such systemscan conform to standards such as Third-Generation Partnership Project 2(3gpp2, or “cdma2000”), Third-Generation Partnership (3gpp, or“W-CDMA”), or Long Term Evolution (“LTE”).

Transmissions from a transmitter to a receiver often employ a degree ofredundancy to guard against errors in the received signals. For example,in a W-CDMA system, information bits corresponding to a transportchannel may be processed using fractional-rate symbol encoding andsymbol repetition (or puncturing). Such encoded symbols may be furthermultiplexed with encoded symbols from one or more other transportchannels, grouped into sub-segments known as slots, and transmitted overthe air. While symbol redundancy techniques may allow accurate recoveryof the information bits in the presence of noise over the channel, suchtechniques also represent a premium in the overall system transmissionpower when signal reception conditions are good. Such a premium mayundesirably reduce the system capacity, i.e., the number of users thesystem can reliably support at any given time.

It would be desirable to provide techniques to allow efficienttransmission of data in a W-CDMA system to minimize transmissionredundancy and increase capacity.

SUMMARY

An aspect of the present disclosure provides a method comprising:receiving symbols corresponding to a composite channel during a firstallotted transmission time interval (TTI), the composite channelcomprising at least two multiplexed transport channels; attempting todecode at least one transport channel prior to receiving all symbols ofthe first TTI; and transmitting an acknowledgement message (ACK) basedon a successful decode, wherein the ACK is operable to ceasetransmission of the symbols during the first TTI.

Another aspect of the present disclosure provides an apparatuscomprising: a receiver configured to receive symbols corresponding to acomposite channel during a first allotted transmission time interval(TTI), the composite channel comprising at least two multiplexedtransport channels; a decoder configured to attempt to decode at leastone transport channel prior to receiving all symbols of the first TTI; atransmitter configured to transmit an acknowledgement message (ACK)based on a successful result of the decoding, wherein the ACK isoperable to cease transmission of the symbols during the first TTI.

Yet another aspect of the present disclosure provides an apparatuscomprising: means for receiving symbols corresponding to a compositechannel during a first allotted transmission time interval (TTI), thecomposite channel comprising at least two multiplexed transportchannels; means for attempting to decode at least one transport channelprior to receiving all symbols of the first TTI; and means fortransmitting an acknowledgement message (ACK) based on a successfuldecode, wherein the ACK is operable to cease transmission of the symbolsduring the first TTI.

Yet another aspect of the present disclosure provides acomputer-readable storage medium storing instructions for causing acomputer to: receive symbols corresponding to a composite channel duringa first allotted transmission time interval (TTI), the composite channelcomprising at least two multiplexed transport channels; attempt todecode at least one transport channel prior to receiving all symbols ofthe first TTI; and transmit an acknowledgement message (ACK) based on asuccessful decode, wherein the ACK is operable to cease transmission ofthe symbols during the first TTI.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a wireless cellular communications system in whichthe techniques of the present disclosure may be applied.

FIG. 2A is a diagram of the signal processing at a Node B for a downlinkdata transmission in accordance with the W-CDMA standard.

FIG. 2B is a diagram of a frame and slot format for the downlink dataphysical channel (DPCH), as defined by the W-CDMA standard.

FIG. 2C is a diagram of a corresponding frame and slot format for theuplink data physical channel (DPCH), as defined by the W-CDMA standard.

FIG. 2D is a diagram of signal processing that may be performed at a UEfor downlink data reception, in accordance with the W-CDMA standard.

FIG. 3 illustrates timing diagrams associated with a prior art signalingscheme for W-CDMA.

FIG. 4 illustrates an exemplary embodiment of a scheme for earlytermination of transmissions for systems operating according to theW-CDMA standard.

FIG. 5 illustrates an exemplary embodiment of an early decoding schemefor a TTI according to the present disclosure.

FIG. 6A illustrates an ACK signaling scheme for early terminationaccording to the W-CDMA standard.

FIG. 6B illustrates an exemplary diagram of a frame and slot format fortransmission of an ACK on the downlink in a W-CDMA system.

FIG. 6C illustrates an exemplary diagram of a frame and slot format fortransmission of an ACK on the uplink in a W-CDMA system.

FIG. 7 illustrates an exemplary embodiment of processing performed at aNode B for early termination of downlink transmissions in response toreceiving an ACK from the UE.

FIG. 8 illustrates a simplified diagram of a prior art scheme fortransmission of a single full-rate AMR frame including class A, B, and CAMR bits over a W-CDMA interface.

FIG. 9 illustrates an exemplary embodiment of a scheme for transmittinga full-rate AMR frame over a W-CDMA interface according to the presentdisclosure.

FIG. 10 illustrates an exemplary embodiment of a system employing atail-biting convolutional code.

FIGS. 11A-11D describe an example radio network operating according toUMTS in which the principles of the present disclosure may be applied.

FIG. 12 illustrates an exemplary embodiment of a table that may bemaintained at a Node B that prioritizes early decoding attempts for theUE's communicating with the Node B on the uplink.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of exemplary embodiments of thepresent invention and is not intended to represent the only exemplaryembodiments in which the present invention can be practiced. The term“exemplary” used throughout this description means “serving as anexample, instance, or illustration,” and should not necessarily beconstrued as preferred or advantageous over other exemplary embodiments.The detailed description includes specific details for the purpose ofproviding a thorough understanding of the exemplary embodiments of theinvention. It will be apparent to those skilled in the art that theexemplary embodiments of the invention may be practiced without thesespecific details. In some instances, well known structures and devicesare shown in block diagram form in order to avoid obscuring the noveltyof the exemplary embodiments presented herein.

In this specification and in the claims, it will be understood that whenan element is referred to as being “connected to” or “coupled to”another element, it can be directly connected or coupled to the otherelement or intervening elements may be present. In contrast, when anelement is referred to as being “directly connected to” or “directlycoupled to” another element, there are no intervening elements present.

Communications systems may use a single carrier frequency or multiplecarrier frequencies. Referring to FIG. 1, in a wireless cellularcommunications system 100, reference numerals 102A to 102G refer tocells, reference numerals 160A to 160G refer to Node B's, and referencenumerals 106A to 1061 refer to User Equipment (UE's). A communicationschannel includes a downlink (also known as a forward link) fortransmissions from a Node B 160 to a UE 106 and an uplink (also known asa reverse link) for transmissions from a UE 106 to a Node B 160. A NodeB is also referred to as a base transceiver system (BTS), an accesspoint, or a base station. The UE 106 is also known as an access station,a remote station, a mobile station or a subscriber station. The UE 106may be mobile or stationary. Furthermore, a UE 106 may be any datadevice that communicates through a wireless channel or through a wiredchannel, for example using fiber optic or coaxial cables. A UE 106 mayfurther be any of a number of types of devices including but not limitedto PC card, compact flash, external or internal modem, or wireless orwireline phone.

Modern communications systems are designed to allow multiple users toaccess a common communications medium. Numerous multiple-accesstechniques are known in the art, such as time division multiple-access(TDMA), frequency division multiple-access (FDMA), space divisionmultiple-access, polarization division multiple-access, code divisionmultiple-access (CDMA), and other similar multiple-access techniques.The multiple-access concept is a channel allocation methodology whichallows multiple users access to a common communications link. Thechannel allocations can take on various forms depending on the specificmulti-access technique. By way of example, in FDMA systems, the totalfrequency spectrum is divided into a number of smaller sub-bands andeach user is given its own sub-band to access the communications link.Alternatively, in CDMA systems, each user is given the entire frequencyspectrum for all of the time but distinguishes its transmission throughthe use of a code.

While certain exemplary embodiments of the present disclosure may bedescribed hereinbelow for operation according to the W-CDMA standard,one of ordinary skill in the art will appreciate that the techniques mayreadily be applied to other digital communications systems. For example,the techniques of the present disclosure may also be applied to systemsbased on the cdma2000 wireless communications standard, and/or any othercommunications standards. Such alternative exemplary embodiments arecontemplated to be within the scope of the present disclosure.

FIG. 2A is a diagram of the signal processing at a Node B for a downlinkdata transmission in accordance with the W-CDMA standard. While signalprocessing of the downlink is specifically described with reference toFIGS. 2A and 2B, corresponding processing performed on the uplink willbe clear to one of ordinary skill in the art, and exemplary embodimentsof the present disclosure in both the downlink and the uplink arecontemplated to be within the scope of the present disclosure.

The upper signaling layers of a W-CDMA system support data transmissionon one or more transport channels to a specific terminal, with eachtransport channel (TrCH) being capable of carrying data for one or moreservices. These services may include voice, video, packet data, and soon, which are collectively referred to herein as “data.”

The data for each transport channel is processed based on one or moretransport formats selected for that transport channel. Each transportformat defines various processing parameters such as a transmission timeinterval (TTI) over which the transport format applies, the size of eachtransport block of data, the number of transport blocks within each TTI,the coding scheme to be used, and so on. The TTI may be specified as 10milliseconds (ms), 20 ms, 40 ms, or 80 ms. Each TTI can be used totransmit a transport block set having a number of equal-sized transportblocks, as specified by the transport format for the TTI. For eachtransport channel, the transport format can dynamically change from TTIto TTI, and the set of transport formats that may be used for thetransport channel is referred to as the transport format set.

As shown in FIG. 2A, the data for each transport channel is provided, inone or more transport blocks for each TTI, to a respective transportchannel processing section 210. Within each processing section 210, eachtransport block is used to calculate a set of cyclic redundancy check(CRC) bits at block 212. The CRC bits are attached to the transportblock and are used by a receiving terminal for block error detection.The one or more CRC coded blocks for each TTI are then seriallyconcatenated together at block 214. If the total number of bits afterconcatenation is greater than the maximum size of a code block, then thebits are segmented into a number of (equal-sized) code blocks. Themaximum code block size is determined by the particular coding scheme(e.g., convolutional, Turbo, or no coding) selected for use for thecurrent TTI, which is specified by the transport format. Each code blockis then coded with the selected coding scheme or not coded at all atblock 216 to generate coded bits.

Rate matching is then performed on the coded bits in accordance with arate-matching attribute assigned by higher signaling layers andspecified by the transport format at block 218. On the uplink, bits arerepeated or punctured (i.e., deleted) such that the number of bits to betransmitted matches the number of available bit positions. On thedownlink, unused bit positions are filled with discontinuoustransmission (DTX) bits at block 220. The DTX bits indicate when atransmission should be turned off and are not actually transmitted.

The rate-matched bits for each TTI are then interleaved in accordancewith a particular interleaving scheme to provide time diversity at block222. In accordance with the W-CDMA standard, the interleaving isperformed over the TTI, which can be selected as 10 ms, 20 ms, 40 ms, or80 ms. When the selected TTI is longer than 10 ms, the bits within theTTI are segmented and mapped onto consecutive transport channel framesat block 224. Each transport channel frame corresponds to the portion ofthe TTI that is to be transmitted over a (10 ms) physical channel radioframe period (or simply, a “frame”).

In W-CDMA, data to be transmitted to a particular terminal is processedas one or more transport channels at a higher signaling layer. Thetransport channels are then mapped to one or more physical channelsassigned to the terminal for a communication (e.g., a call). In W-CDMA,a downlink dedicated physical channel (downlink DPCH) is typicallyassigned to each terminal for the duration of a communication. Thedownlink DPCH is used to carry the transport channel data in atime-division multiplexed manner along with control data (e.g., pilot,power control information, and so on). The downlink DPCH may thus beviewed as a multiplex of a downlink dedicated physical data channel(DPDCH) and a downlink dedicated physical control channel (DPCCH), asdescribed below. The transport channel data is mapped only to the DPDCH,while the DPCCH includes the physical layer signaling information.

The transport channel frames from all active transport channelprocessing sections 210 are serially multiplexed into a coded compositetransport channel (CCTrCH) at block 232. DTX bits may then be insertedinto the multiplexed radio frames such that the number of bits to betransmitted matches the number of available bit positions on one or more“physical channels” to be used for the data transmission at block 234.If more than one physical channel is used, then the bits are segmentedamong the physical channels at block 236. The bits in each frame foreach physical channel are then further interleaved to provide additionaltime diversity at block 238. The interleaved bits are then mapped to thedata portions (e.g., DPDCH) of their respective physical channels atblock 240. The bits of the physical channel are spread using orthogonalvariable spreading factor (OVSF) codes at block 242, modulated at block243, and subsequently segmented into physical channel radio frames 244a, 244 b, etc. It will be appreciated that the spreading factor (SF)employed may be chosen based on how many bits are to be transmitted in aframe.

Note in this specification and in the claims, a “composite channel” maybe defined as any transmission (e.g., DPCH TX) that contains datamultiplexed from two or more transport channels.

FIG. 2B is a diagram of a frame and slot format for the downlink dataphysical channel (DPCH), as defined by the W-CDMA standard. The data tobe transmitted on the downlink DPCH is partitioned into radio frames,with each radio frame being transmitted over a (10 ms) frame thatcomprises 15 slots labeled as slot 0 through slot 14. Each slot isfurther partitioned into a number of fields used to carry user-specificdata, signaling, and pilot, or a combination thereof.

As shown in FIG. 2B, for the downlink DPCH, each slot includes datafields 420 a and 420 b (Data 1 and Data 2), a transmit power control(TPC) field 422, a transport format combination indicator (TFCI) field424, and a pilot field 426. Data fields 420 a and 420 b are used to senduser-specific data. The TPC field 422 is used to send power controlinformation to direct the terminal to adjust its uplink transmit powereither up or down to achieve the desired uplink performance whileminimizing interference to other terminals. TFCI field 424 is used tosend information indicative of the transport format of the downlink DPCHand a downlink shared channel DSCH, if any, assigned to the terminal.Pilot field 426 is used to send a dedicated pilot.

FIG. 2C is a diagram of a corresponding frame and slot format for theuplink data physical channel (DPCH), as defined by the W-CDMA standard.As shown in FIG. 2C, for the uplink DPCH, each slot includes a datafield 280 (Data), a pilot field 282, a transport format combinationindicator (TFCI) field 284, a feedback information field (FBI) 286, anda transmit power control (TPC) field 288. FBI field 286 may supportfeedback for use in, e.g., closed-loop transmit diversity.

FIG. 2D is a diagram of signal processing that may be performed at a UEfor downlink data reception, in accordance with the W-CDMA standard. Oneof ordinary skill in the art will appreciate that the techniquesdescribed may be readily modified to support signal processing at a NodeB for the uplink transmission, in accordance with W-CDMA or any otherstandard.

The signal processing shown in FIG. 2D is complementary to that shown inFIG. 2A. Initially, the symbols for a physical channel radio frame maybe received at block 250. The symbols are demodulated at block 251 anddespread at block 252. Extraction of the symbols corresponding to thedata channel is performed at block 253. The symbols of each frame foreach physical channel are de-interleaved at block 254, and thede-interleaved symbols from all physical channels are concatenated atblock 255. Removal of DTX bits is performed at block 256. The symbolsare then demultiplexed into various transport channels at block 258. Theradio frames for each transport channel are then provided to arespective transport channel processing section 260.

Within each transport channel processing section 260, the transportchannel radio frames are concatenated into transport block sets at block262. Each transport block set includes one or more transport channelradio frames depending on the respective TTI. The symbols within eachtransport block set are de-interleaved at block 264, and non-transmittedsymbols are removed at block 266. Inverse rate matching (or de-ratematching) is then performed to accumulate repeated symbols and insert“erasures” for punctured symbols at block 268. Each coded block in thetransport block set is then decoded at block 270, and the decoded blocksare concatenated and segmented into one or more transport blocks atblock 272. Each transport block is then checked for error using the CRCbits attached to the transport block at block 274. For each transportchannel, one or more decoded transport blocks are provided for each TTI.In certain prior art implementations, the decoding of coded blocks atblock 270 may commence only after all physical channel radio frames ofthe corresponding TTI are received.

FIG. 3 illustrates timing diagrams associated with a prior art signalingscheme for W-CDMA. It will be appreciated that the signaling schemeshown in FIG. 3 may describe either the downlink or the uplink.

In FIG. 3, DPCH slots of TrCH's A, B, and C are transmitted at 300. Eachtransport channel has a TTI of 20 ms, each spanning 30 slots, each slothaving a slot identification number (slot ID#) 0 to 29. The slots of theDPCH are received at 310. In the prior art scheme, all 30 slots of a TTIare received before attempting to decode a corresponding transportchannel. For example, slot ID#'s 0 through 29 of TTI #0 are receivedbefore attempting to decode any of TrCH's A, B, and C at 330. Followinga decoding time TD, TrCH's A, B, and C are successfully decoded at 340.Note while decoding of TrCH's A, B, and C is performed, the transmittedsymbols for TTI #1 may concurrently be received at the receiver.

In accordance with the present disclosure, early decoding andtermination techniques for W-CDMA as described hereinbelow may allow acommunications system to operate more efficiently and save transmissionpower, thereby increasing system capacity.

FIG. 4 illustrates an exemplary embodiment of a scheme for earlytermination of transmissions for systems operating according to theW-CDMA standard. Note the exemplary embodiment is shown for illustrativepurposes only, and is not meant to limit the scope of the presentdisclosure to systems based on W-CDMA. One of ordinary skill in the artwill also appreciate that specific parameters such as number andtransport format of transport channels, slot or frame timings, slotintervals and timings at which decoding attempts are made, etc., areshown for illustrative purposes only, and are not meant to limit thescope of the present disclosure.

In FIG. 4, DPCH slots of TrCH's A, B, and C are transmitted at 400. Thetransmitted slots are received at 410 by a receiver. According to thepresent disclosure, not all slots of a TTI need to be received beforeattempting to decode a corresponding transport channel(s). For example,a decoding attempt of TrCH A of TTI #0 occurs at 421, after receivingslot ID#19 of TTI #0. Following a decoding time TD_(A), TrCH A issuccessfully decoded at 422. Similarly, a decoding attempt of TrCH Boccurs at 423, after receiving slot ID#24, and TrCH B is thereaftersuccessfully decoded following a decoding time TD_(B) at 424. A decodingattempt of TrCH C occurs at 425, after receiving slot ID#29, and TrCH Cis thereafter successfully decoded following a decoding time TD_(C).Note while specific time intervals are shown for TD_(A), TD_(B), andTD_(C) in FIG. 4, it will be appreciated that the present techniques maybe applied to accommodate any arbitrary decoding times.

It will be appreciated that while the slots received prior to thedecoding attempts of both TrCH's A and B at 421 and 423 correspond toonly a portion of the total slots for the entire TTI, “early” decodingof the entire TTI using only the received slots may nevertheless beattempted on TrCH's A and B. Such early decoding attempts may have asubstantial chance of decoding success due to, e.g., redundancy in thereceived symbols introduced by fractional rate encoding and/orrepetition, e.g., at blocks 216 and 218 of FIG. 2A, and/or time- orother-dimensional diversity achieved via interleaving at blocks 222 and238 of FIG. 2A.

Returning to FIG. 4, following a time T_ACK after TrCH A is successfullydecoded at 422, an acknowledgment message (ACK) for TrCH A is sent tothe DPCH transmitting side (TX) at 431. In an exemplary embodiment, theACK may serve to notify the DPCH TX that the corresponding transportchannel has been correctly decoded based on the already transmittedslots, and that further transmission of the remaining slot(s) of thetransport channel may be unnecessary. In the exemplary embodiment shown,after receiving the ACK for TrCH A, the DPCH TX terminates slottransmission of TrCH A for the remainder of TTI #0, starting with slotID#24. Transmission of TrCH A recommences at the start of the next TTI,TTI #1. Similarly, the DPCH TX terminates slot transmission of TrCH Bstarting with slot ID#28 in response to receiving an ACK for TrCH B sentat 432, and recommences transmission of TrCH B at the start of the nextTTI, TTI #1.

It will be appreciated that by terminating slot transmission for atransport channel prior to the end of a TTI, the potential interferenceto other users may be significantly reduced, thereby increasing systemcapacity.

One of ordinary skill in the art will appreciate that the total timefrom: a) receiving a slot at the DPCH RX designated for a decodingattempt, to b) sending an ACK to terminate transmissions at the DPCH TX,includes the time intervals TD_(A) and T_ACK as described hereinabove,and may be determined by, e.g., the available computational resourcesfor decoding. In an exemplary embodiment, such total time may bedesigned to be 3 slots.

In an exemplary embodiment, the time intervals separating decodingattempts for each transport channel may be chosen as a design parameter.For example, a decoding attempt for any particular transport channel maybe made every one, two, or any number of slots. Alternatively, decodingattempts for any transport channel may be made aperiodically throughoutthe duration of the TTI. It will be appreciated that increasing thefrequency of decoding attempts will generally increase the likelihoodthat a transport channel is decoded at the earliest possibleopportunity, at the cost of greater required computational bandwidth. Inan exemplary embodiment, decoding attempts of one or more transportchannels may be performed every 3 slots, or 2 ms.

In an exemplary embodiment, decoding attempts of a transport channel maybe offset in time from decoding attempts of another transport channel.For example, in FIG. 4, the decoding attempt of TrCH A is performedafter receiving slot ID#19, while the decoding attempt of TrCH B isperformed after receiving slot ID#24. This may advantageously allow asingle decoder to be reused for decoding attempts of multiple transportchannels, by serially allocating the use of the decoder in time to thetwo transport channels. In an alternative exemplary embodiment, ifgreater decoding resources (e.g., two or more independent Viterbidecoders) are available, decoding attempts of different transportchannels may be performed in parallel, e.g., decoding attempts of two ormore transport channels may be concurrently performed after receivingthe same slot. Such exemplary embodiments are contemplated to be withinthe scope of the present disclosure.

In the exemplary embodiment shown, a separate ACK is sent for earlytermination of each transport channel. One of ordinary skill in the artwill appreciate that alternatively, a single ACK may signal earlytermination of more than one transport channel, as agreed upon bytransmitter and receiver. Such alternative exemplary embodiments arecontemplated to be within the scope of the present disclosure.

It will be appreciated that ACK channels for individual transportchannels may be multiplexed in time, e.g., using a DPCCH portion of atransmission from the DPCH RX 410 to the DPCH TX 400, or in code, e.g.,by allocating a separate Walsh code for each transport channel. PossibleACK signaling mechanisms in W-CDMA are described later herein.

FIG. 5 illustrates an exemplary embodiment of an early decoding schemefor a TTI according to the present disclosure. Note FIG. 5 is shown forillustrative purposes only, and is not intended to restrict the scope ofthe present disclosure to any particular exemplary embodiments shown.

In FIG. 5, at block 501, a slot index n is initialized to n=0.

At block 510, symbols are received for slot ID#n.

At block 520, the symbols received up to slot ID#n are processed. In anexemplary embodiment, such processing may include blocks 252-258 asdescribed with reference to FIG. 2D, e.g., de-spreading, secondde-interleaving, transport channel de-multiplexing, etc. In an exemplaryembodiment, such processing may further include transportchannel-specific processing such as blocks 262-268 described withreference to FIG. 2D, e.g., first de-interleaving, inverse ratematching, etc.

Following block 520, n may be incremented at block 525, and reception ofsymbols for the next slot may proceed at block 510. Further followingblock 520, decoding attempts may be performed on a per-transport channelbasis for one or more transport channels, as described with reference toblocks 530-560. One of ordinary skill in the art will appreciate thatthe techniques may be applied to any configuration of one or moretransport channels.

At block 530.1, it is determined whether a decoding attempt should beperformed for TrCH X1. If so, then operation proceeds to block 540.1. Inan exemplary embodiment, the determination of whether decoding should beattempted may be based on the slot ID#of a slot that has been justreceived. For example, a decoding attempt for TrCH X1 may be made every1, 2, or more slots starting with a first slot ID#x. Furthermore,decoding attempts for one transport channel may be offset from decodingattempts for other transport channels, as earlier described herein.Other schemes for determining whether decoding attempts should beperformed will be clear to one of ordinary skill in the art in light ofthe present disclosure.

At block 540.1, decoding is performed for the symbols of TrCH X1processed, e.g., at block 520, up to slot ID# n.

At block 550.1, it is determined whether the decoding performed at block540.1 was a success. In an exemplary embodiment, decoding success may bedetermined based on whether a decoded CRC of one or more transportblocks of the transport channel is correctly verified. It will beappreciated that for transport channels having transport formats notspecifying the use of a CRC, other metrics may be used to determinedecoding success, e.g., an energy metric as computed by a decoder forthe decoded block. If the decoding was a success, then operationproceeds to block 560.1, else operation returns to block 530.1.

At block 560.1, an ACK is transmitted for TrCH X1 at the next availableopportunity. The mechanism for ACK transmission may utilize thetechniques described hereinbelow with reference to FIGS. 6A, 6B, and 6C.

FIG. 6A illustrates an ACK signaling scheme for early terminationaccording to the W-CDMA standard. In FIG. 6A, one or more ACK bits areprovided to an on-off keying (OOK) modulation block 610. A poweradjustment factor PO_(ACK) is multiplied with the modulated ACK symbolsat 612. One or more TPC bits are provided to a quadrature phase-shiftkeying (QPSK) block 620, and the modulated TPC symbols are multiplied bya power adjustment factor PO_(TPC) at 622. Similarly, one or more pilotbits DP are provided to a QPSK block 630, and the modulated TPC symbolsare multiplied by a power adjustment factor PO_(DP) at 632. Thepower-adjusted symbols are provided to a multiplexing block 614, whichoutputs a waveform wherein the symbols are multiplexed to generate aDPCCH symbol stream. In exemplary embodiments, the symbols may bemultiplexed in time, or code, etc.

It will be appreciated that in alternative exemplary embodiments,control bits not shown may also be processed and multiplexed onto theDPCCH symbol stream, e.g., TFCI bits, etc.

In FIG. 6A, data source bits are provided to a data source bitsprocessing block 640. In an exemplary embodiment, block 640 may performoperations described with reference to blocks 212-242 of FIG. 2A. Theprocessed bits are provided to a QPSK modulation block 642 to generate aDPDCH symbol stream. The DPCCH and DPDCH symbol streams are in turnmultiplexed by a multiplexer 650 to generate the symbols for the DPCH.

In an exemplary embodiment, to accommodate the extra symbols for theACK, the number of symbols allocated to the dedicated pilot bits DP maybe correspondingly reduced, i.e., the ACK may be multiplexed with DP intime. To maintain a constant total energy allocated for the pilot DP,the power offset PO_(DP) applied to DP may be correspondingly increased.

The scheme shown in FIG. 6A may be applied to downlink transmissionsaccording to the W-CDMA standard. The ACK message shown may betransmitted by, e.g., a UE on an uplink, and received by a Node B on theuplink to terminate the Node B's downlink transmissions of one or moretransport channels to the UE.

FIG. 6B illustrates an exemplary diagram of a frame and slot format fortransmission of an ACK on the downlink in a W-CDMA system. The ACKtransmission shown may be used on the downlink for early termination ofuplink transmissions. In particular, the ACK is shown multiplexed intime with the pilot portion in the downlink DPCCH. In an exemplaryembodiment, the power allotted to the ACK portion may be fixed at apredefined offset relative to, e.g., the pilot portion, to ensure asatisfactory error rate for ACK reception on the downlink.

In an alternative exemplary embodiment (not shown), the pilot portionmay be omitted altogether, and the ACK may be provided in the timeinterval otherwise allocated to the pilot. Such alternative exemplaryembodiments are contemplated to be within the scope of the presentdisclosure.

FIG. 6C illustrates an exemplary diagram of a frame and slot format fortransmission of an ACK on the uplink in a W-CDMA system. The ACKtransmission shown may be used for early termination of downlinktransmissions. In particular, the ACK may again be multiplexed with thepilot, e.g., e.g., in time or in code, on the DPCCH of an uplink frame.

In alternative exemplary embodiments (not shown), an ACK may beseparately provided on a separate channel independent of the DPCCH andDPDCH of an uplink frame. For example, a separate code channel may beassigned to an ACK. Furthermore, when multiple ACK's are provided formultiple transport channels, such multiple ACK's may be, e.g.,multiplexed in code (by providing a separate code channel for each ACK)or multiplexed in time on a single code channel. Such alternativeexemplary embodiments are contemplated to be within the scope of thepresent disclosure.

While specific exemplary embodiments have been described foraccommodating ACK messaging in the present W-CDMA physical channelformats, one of ordinary skill in the art will appreciate that otherexemplary embodiments are possible. In an alternative exemplaryembodiment (not shown), any portion of the time intervals allocated totransmission of control symbols (on either uplink or downlink) may bereplaced by ACK messaging symbols for any pre-designated slot or slots.The power allocated to such control symbols may be correspondinglyupwardly adjusted to compensate for any decrease in total energy of thecontrol symbols pilot due to the ACK messaging.

FIG. 7 illustrates an exemplary embodiment of processing performed at aNode B for early termination of downlink transmissions in response toreceiving an ACK from the UE. One of ordinary skill in the art willappreciate that similar techniques may be adopted by the UE for earlytermination of uplink transmissions in response to receiving an ACK fromthe Node B. Such alternative exemplary embodiments are contemplated tobe within the scope of the present disclosure.

In FIG. 7, an ACK reception module 710 at the Node B receives an ACKsent from a UE, wherein the ACK indicates that one or more of TrCH's A,B, and C have been correctly received by the UE. The ACK receptionmodule 710 determines the transport channel that the ACK corresponds to,and signals those transport channels to a selective TrCH puncturingmodule 720. The selective TrCH puncturing module 720 is configured topuncture those bits corresponding to the acknowledged (ACK'ed) transportchannels at the output of the second interleaving block 238. It will beappreciated that the process of puncturing may include replacing bitsdesignated for transmission with “erasure” or “discontinuoustransmission” (DTX) bits. The output stream of the selective puncturingmodule 720 is provided to the physical channel mapping block 240 forfurther downlink processing, as previously described herein withreference to FIG. 2A.

One of ordinary skill in the art will appreciate that the selectivepuncturing module 720 may be pre-programmed to identify which bitsoutput by the second interleaving block 238 correspond to a particulartransport channel, and may incorporate knowledge of, e.g., the first andsecond interleaving parameters, rate matching parameters, encoding,etc., of all the transport channels available.

Note in alternative exemplary embodiments, the ACK reception module 710and the selective TrCH puncturing module 720 may readily be modified toaccommodate fewer or more transport channels than shown in FIG. 7.Furthermore, the selective TrCH puncturing module 720 need not beprovided after the second interleaver 710, and may instead be providedanywhere in the signal processing chain, as long as the bitscorresponding to the particular TrCH ACK'ed are correctly selected. Suchalternative exemplary embodiments are contemplated to be within thescope of the present disclosure.

In an exemplary embodiment, the early termination techniques describedherein may be applied to voice communications using the adaptivemulti-rate (AMR) speech codec according to the W-CDMA standard. In avoice communications system, a speech codec is often employed to encodea voice transmission using one of a plurality of variable encodingrates. The encoding rate may be selected based on, e.g., the amount ofspeech activity detected during a particular time interval. In W-CDMA,speech transmissions may be encoded using an adaptive multi-rate (AMR)codec, which encodes speech using one of a plurality of different bitrates or “AMR modes.” In particular, the AMR codec may support any of aplurality of full-rate (“FULL”) bit-rates ranging from 4.75 kbps (orkilobits per second) to 12.2 kbps, and for periods of silence, a silenceindicator (“SID”) bit-rate of 1.8 kbps, and frames of discontinuoustransmission (DTX or “NULL”) of 0 kbps.

It will be appreciated that full-rate AMR bits may be furtherpartitioned into “class A bits” that are most sensitive to error, “classB bits” that are less sensitive to error, and “class C bits” that areleast sensitive to error. In an exemplary embodiment, such class A, B,and C bits may be assigned to transport channels TrCH A, B, and C,respectively, for transmission over the air using the W-CDMA uplink ordownlink interface. (See, e.g., the description of the W-CDMA downlinkinterface with reference to FIG. 2A hereinabove.) In an exemplaryembodiment, the transport formats of TrCH A, B, and C may be definedsuch that class A bits are afforded the highest level of errorprotection (e.g., by setting encoding, CRC, and/or rate matchingparameters), class B bits less error protection, and class C bitsafforded the least error protection. In an exemplary embodiment, the TTIof each of the AMR transport formats may be defined as 20 ms.

FIG. 8 illustrates a simplified diagram of a prior art scheme fortransmission of a single full-rate AMR frame including class A, B, and CAMR bits over a W-CDMA interface. It will be appreciated that, for easeof illustration, the processing shown in FIG. 8 omits certain details,e.g., the complete signal processing chain for TrCH's A, B, and C. In anexemplary embodiment, the schemes illustrated in FIGS. 8 and 9 may beapplied on the uplink of a W-CDMA system.

In FIG. 8, the AMR class A, B, and C bits are assigned to transportchannels A, B, and C, respectively. The bits of each transport channelare provided to corresponding transport channel processing blocks 830,832, and 834. In an implementation, the transport format for transportchannel A (corresponding to the AMR class A bits) specifies a 12-bit CRCfor the transport blocks of TrCH A, while transport blocks TrCH's B andC do not contain CRC's.

Following blocks 830, 832, and 834, radio frame segmentation isperformed at blocks 831, 833, and 835, respectively. For example, bitscorresponding to AMR class A are segmented into a portion A1 for a firstradio frame and A2 for a second radio frame, AMR class B bits aresegmented into B1 and B2, and AMR class C bits are segmented into C1 andC2. The bits A1 are multiplexed with B1 and C1 to generate a CCTrCH840.1, and the bits A2, B2, and C2 are likewise multiplexed to generatea CCTrCH 840.2. Second interleaving 850.1, 850.2 is separately performedfor each of the CCTrCH's. The data for each frame is spread using aspreading factor of 64 at 860.1, 860.2 to generate frames 1 and 2.

In an implementation, per the W-CDMA standard, the uplink spreadingfactor is limited to at least 64.

According to the early decoding techniques described herein, thereceiver may attempt early decoding on each of frames 1 and 2 generatedaccording to the scheme shown in FIG. 8. In practice, the likelihood ofsuccessfully decoding a full two-frame TTI based on receiving only afirst frame, e.g., after receiving 15 slots, may be quite low. Furtherdisclosed herein are techniques to increase the likelihood ofsuccessfully decoding a full TTI at the earliest possible time.

FIG. 9 illustrates an exemplary embodiment of a scheme for transmittinga full-rate AMR frame over a W-CDMA interface according to the presentdisclosure. In FIG. 9, AMR class A, B, and C bits are assigned totransport channels A, B, and C, respectively. The bits of each transportchannel are provided to corresponding transport channel processingblocks 930, 932, and 934. In an exemplary embodiment, the coding rate ofone or more transport channels may be reduced relative to the prior artscheme shown in FIG. 8, i.e., the number of coded symbols for eachinformation symbol may be increased.

Following blocks 930, 932, and 934, segmentation is performed at blocks931, 933, and 935, respectively, to generate bits A1, A2, B1, B2, C1,and C2 at 940. These bits are collectively provided to a 20-ms secondinterleaver 950. In an exemplary embodiment, the second interleaver 950is modified from the prior art W-CDMA second interleaver 850 in that thesecond interleaver 950 is designed to interleave bits over 20 ms ratherthan 10 ms. This may advantageously distribute the encoded bits of eachAMR class more uniformly over an entire TTI, thereby leading to greaterlikelihood of decoding one or more classes of the AMR bits at an earliertime.

Radio frame segmentation 952 is performed at the output of the 20-mssecond interleaver 950 to separate the second-interleaved bits intofirst and second radio frames. The bits are spread at blocks 960.1 and960.2. In an exemplary embodiment, the spreading at 960.1 and 960.2 isperformed using a spreading factor less than the spreading factoremployed at blocks 860.1 and 860.2 in the prior art AMR transmissionscheme. It will be appreciated that reducing the spreading factor allowseach frame to accommodate an increased number of bits resulting from,e.g., reducing the coding rate at transport channel processing blocks930, 932, and 934, as earlier described herein. By simultaneouslyreducing the coding rate and spreading factor, and further introducing20-ms second interleaving, it will be appreciated that the likelihood ofsuccessful decoding at an earlier time may be improved.

While FIG. 9 illustrates an exemplary embodiment wherein the reductionin coding rate and spreading factor is implemented in conjunction with20-ms second interleaving, it will be appreciated that in alternativeexemplary embodiments, the two features may be implemented separately.It will be further appreciated that the spreading factors referred to inFIGS. 8 and 9 are for illustrative purposes only. In alternativeexemplary embodiments, other spreading factors may be readily employed,and such alternative exemplary embodiments are contemplated to be withinthe scope of the present disclosure.

In an exemplary embodiment, early decoding of TrCH's A, B, and Ccorresponding to AMR classes A, B, and C may proceed as earlierdescribed herein with reference to FIG. 4. In particular, severaloptions exist for coordinating the early decoding attempts of themultiple transport channels, some of which are explicitly described asfollows for illustrative purposes.

In a first exemplary embodiment (also referred to herein as “ET-A”),early decoding of the AMR class A bits may be attempted every 3 slots,or 2 ms, starting with any slot received. Once the class A bits aresuccessfully decoded, e.g., based on CRC check, an ACK for TrCH A may besent, and transmission of class A bits may be terminated. AMR class Band C bits may continue to be transmitted until the end of the TTI.

In a second exemplary embodiment (also referred to herein as “ET-A-B”),the transport formats of TrCH's A and B, corresponding to AMR class Aand class B, may both specify inclusion of a CRC, and thus earlydecoding may be attempted on both TrCH's A and B. In certain exemplaryembodiments, early decoding attempts of TrCH A may be offset in timefrom early decoding attempts of TrCH B. Alternatively, decoding attemptsof TrCH's A and B may be concurrently performed at a receiver afterreceiving the same slot.

Note while an exemplary embodiment has been described with reference toFIG. 9 wherein AMR class A, B, and C bits are assigned to TrCH's A, B,and C, respectively, alternative exemplary embodiments may employalternative assignments of AMR classes to transport channels. In a thirdexemplary embodiment (also referred to herein as “ET-AB”), AMR class Aand B bits may be assigned to a single transport channel, e.g., TrCH A,while AMR class C bits may be assigned to a separate transport channel,e.g., TrCH B. In this case, early decoding and termination of TrCH Awould result in early termination of both AMR class A and B bits. Suchalternative exemplary embodiments are contemplated to be within thescope of the present disclosure.

In an alternative exemplary embodiment, to further reduce the powerrequired to transmit certain ARM classes over the W-CDMA interface, atransport format supporting a tail-biting convolutional coding schemeknown in the art may be added to those already supported by the W-CDMAstandard. It will be appreciated that a tail-biting convolutional codeallows the tail bits associated with the convolutional code to beomitted by pre-loading the initial state of the convolutional code shiftregister with the expected ending state, thereby decreasing the overheadnumber of bits.

FIG. 10 illustrates an exemplary embodiment of a system employing atail-biting convolutional code. In FIG. 10, bits for a TrCH X areprovided to a TrCH/PhCH processing block 1010. Block 1010 may encode theTrCH X bits using a tail-biting convolutional code encoder 1015. Forexample, the tail-biting convolutional code encoder 1015 may be providedas the channel coding block 216 in FIG. 2.

Following block 1010, a signal is transmitted over the channel 1019, andprovided to PhCH/TrCH processing block 1020. Block 1020 includes a block1030 that determines whether early decoding should be attempted based onthe current slot received. If so, the received symbols are provided tothe tail-biting convolutional code decoder 1040, which implements any ofa variety of tail-biting convolutional code decoding schemes known inthe art. At block 1050, it is determined whether the decoding issuccessful. If yes, the TTI is declared successfully declared, and thedecoded bits are provided. If no, then operation returns to block 1030to wait for the next early decoding opportunity.

It will be appreciated that by omitting the tail bits associated with aconventional convolutional code, less data needs to be transmitted overthe channel in the case of a tail-biting convolutional code, therebygenerating less interference to other users. It will be furtherappreciated that repeated early decoding attempts of a tail-bitingconvolutional code may take advantage of the fact that the ending stateof a previous early decoding attempt is expected to be equal to theinitial state of a subsequent early decoding attempt of the sametransport channel, thereby potentially saving computational resources.

In an exemplary embodiment, a transport format for one or more classesof AMR bits may specify that a tail-biting convolutional code be used toencode the class of bits. For example, in an exemplary embodiment (alsoreferred to herein as “ET-A-B-TB”), the transport formats of TrCH A forAMR class A bits and TrCH B for AMR class B bits may both specify theinclusion of a CRC, while the transport formats of TrCH B and TrCH C forAMR class C bits may both specify that a tail-biting convolutional codebe used for the encoding scheme. At the receiver, early decoding may beattempted on TrCH A and TrCH B according to the principles earlierdescribed. In an alternative exemplary embodiment (also referred toherein as “ET-A-B-TB-Mod”), only the transport format of TrCH C for AMRclass C bits may specify that a tail-biting convolutional code be usedfor the encoding scheme.

One of ordinary skill in the art will appreciate that the combinationsof the transport formats described are given for illustrative purposesonly, and that alternative exemplary embodiments may readily employother combinations of the features described for transmission of the AMRbits according to the W-CDMA standard. Such alternative exemplaryembodiments are contemplated to be within the scope of the presentdisclosure.

In an exemplary embodiment, the number of source bits for each transportchannel, the number of CRC bits, and the number of tail bits for variousAMR transmission techniques described herein may be chosen as follows(Table 1):

Number of Source Number of Number of bits (AMR class) CRC bits tail bitsBaseline and 81 (A) 12 8 ET-A 103 (B) 0 8 60 (C) 0 8 ET-AB 184 (AB) 16 860 (C) 0 8 ET-A-B 81 (A) 12 8 103 (B) 12 8 60 (C) 0 8 ET-A-B-TB 81 (A)12 8 103 (B) 12 0 60 (C) 0 0 ET-A-B-TB- 81 (A) 12 8 Mod 103 (B) 12 8 60(C) 0 0

In an exemplary embodiment, to further reduce transmission power in thesystem, the DPDCH portion of an AMR NULL packet may be entirely blanked,or inserted with DTX bits, on either the downlink or the uplink. In thiscase, no decoding would be performed at the receiver on such NULLpackets. In conjunction therewith, outer-loop power control (OLPC)schemes at the receiver may be based only on received AMR FULL and SIDpackets, e.g., an OLPC scheme is not updated when an AMR NULL packet isreceived.

In an alternative exemplary embodiment, in conjunction with the earlytermination techniques described herein, the power control rate of thedownlink or uplink may be further reduced. For example, rather thansending a power control command (e.g., in a TPC field of a slot) inevery slot, a power control command may be sent once every two or moreslots. In an exemplary embodiment, the DPCCH portion of an AMR NULLpacket on the uplink may be gated according to a gating patterndetermined by a power control rate on the downlink. For example, when750 Hz power control is applied on the downlink, the uplink DPCCH may begated (i.e., selectively turned off) once every other slot whentransmitting AMR NULL packets. In alternative exemplary embodiments, ifthe power control rate of the downlink is even further slowed down whentransmitting AMR NULL packets (e.g., <750 Hz), then the uplink DPCCH maybe gated even more frequently (e.g., uplink DPCCH may be turned on onlyonce every four or five slots). It will be appreciated that furtherconsiderations affecting how often the DPCCH may be gated include howreliably the uplink searcher can function, how reliably the uplinkoverhead channels can be decoded, and the configuration of the powercontrol bit transmission waveforms on the uplink. Such exemplaryembodiments are contemplated to be within the scope of the presentdisclosure.

Further described herein with reference to FIGS. 11A-11D is an exampleradio network operating according to UMTS in which the principles of thepresent disclosure may be applied. Note FIGS. 11A-11D are shown forillustrative background purposes only, and are not meant to limit thescope of the present disclosure to radio networks operating according toUMTS.

FIG. 11A illustrates an example of a radio network. In FIG. 11A, Node Bs110, 111, 114 and radio network controllers 141-144 are parts of anetwork called “radio network,” “RN,” “access network,” or “AN.” Theradio network may be a UMTS Terrestrial Radio Access Network (UTRAN). AUMTS Terrestrial Radio Access Network (UTRAN) is a collective term forthe Node Bs (or base stations) and the control equipment for the Node Bs(or radio network controllers (RNC)) it contains which make up the UMTSradio access network. This is a 3 G communications network which cancarry both real-time circuit-switched and IP-based packet-switchedtraffic types. The UTRAN provides an air interface access method for theuser equipment (UE) 123-127. Connectivity is provided between the UE andthe core network by the UTRAN. The radio network may transport datapackets between multiple user equipment devices 123-127.

The UTRAN is connected internally or externally to other functionalentities by four interfaces: Iu, Uu, Iub and Iur. The UTRAN is attachedto a GSM core network 121 via an external interface called Iu. Radionetwork controllers (RNC's) 141-144 (shown in FIG. 11B), of which 141,142 are shown in FIG. 11A, support this interface. In addition, the RNCmanages a set of base stations called Node Bs through interfaces labeledIub. The Iur interface connects two RNCs 141, 142 with each other. TheUTRAN is largely autonomous from the core network 121 since the RNCs141-144 are interconnected by the Iur interface. FIG. 11A discloses acommunication system which uses the RNC, the Node Bs and the Iu and Uuinterfaces. The Uu is also external and connects the Node B with the UE,while the Iub is an internal interface connecting the RNC with the NodeB.

The radio network may be further connected to additional networksoutside the radio network, such as a corporate intranet, the Internet,or a conventional public switched telephone network as stated above, andmay transport data packets between each user equipment device 123-127and such outside networks.

FIG. 11B illustrates selected components of a communication network100B, which includes a radio network controller (RNC) (or base stationcontroller (BSC)) 141-144 coupled to Node Bs (or base stations orwireless base transceiver stations) 110, 111, and 114. The Node Bs 110,111, 114 communicate with user equipment (or remote stations) 123-127through corresponding wireless connections 155, 167, 182, 192, 193, 194.The RNC 141-144 provides control functionalities for one or more NodeBs. The radio network controller 141-144 is coupled to a public switchedtelephone network (PSTN) 148 through a mobile switching center (MSC)151, 152. In another example, the radio network controller 141-144 iscoupled to a packet switched network (PSN) (not shown) through a packetdata server node (“PDSN”) (not shown). Data interchange between variousnetwork elements, such as the radio network controller 141-144 and apacket data server node, can be implemented using any number ofprotocols, for example, the Internet Protocol (“IP”), an asynchronoustransfer mode (“ATM”) protocol, T1, E1, frame relay, and otherprotocols.

The RNC fills multiple roles. First, it may control the admission of newmobiles or services attempting to use the Node B. Second, from the NodeB, or base station, point of view, the RNC is a controlling RNC.Controlling admission ensures that mobiles are allocated radio resources(bandwidth and signal/noise ratio) up to what the network has available.It is where the Node B's Iub interface terminates. From the UE, ormobile, point of view, the RNC acts as a serving RNC in which itterminates the mobile's link layer communications. From a core networkpoint of view, the serving RNC terminates the Iu for the UE. The servingRNC also controls the admission of new mobiles or services attempting touse the core network over its Iu interface.

In an exemplary embodiment, each Node B may maintain a table whichprioritizes early decoding attempts on the uplink among different UE'sbased on predetermined criteria. For example, a UE in soft hand-off(SHO) may cause more interference to other cells than a UE not in SHO,and therefore, system capacity may be improved by more frequentlyattempting to decode such UE's (in SHO). FIG. 12 illustrates anexemplary embodiment of a table 1200 that may be maintained at a Node Bthat prioritizes early decoding attempts for the UE's communicating withthe Node B on the uplink. In FIG. 12, each UE is represented by acorresponding UE index, and is also mapped to a corresponding allocationindicator. The allocation indicator may specify how often early decodingattempts are to be performed for each UE at the Node B. For example, forUE #1, an allocation indicator of 10 may specify that early decoding maybe attempted on UE #1 ten times over the course of a 20-ms TTI, while anallocation indicator of 5 may specify that early decoding may beattempted on UE #2 five times over 20 ms. One of ordinary skill in theart will appreciate that alternative embodiments of allocationindicators may also be readily derived that represent the suggestedfrequency of early decoding attempts, e.g., a number of slots betweenevery early decoding attempt, etc. The table in FIG. 12 may bemaintained at an RNC, and provided to Node B's. Alternatively, each NodeB can maintain a separate table, and also respond to requests from otherNode B's to, e.g., adjust the early decoding priority of the UE's itservices.

It will be appreciated that such techniques may be readily applied bythe UE on the downlink as well to, e.g., prioritize early decodingattempts of different channels being received by the UE.

For an air interface, UMTS most commonly uses a wideband spread-spectrummobile air interface known as wideband code division multiple access (orW-CDMA). W-CDMA uses a direct sequence code division multiple accesssignaling method (or CDMA) to separate users. W-CDMA (Wideband CodeDivision Multiple Access) is a third generation standard for mobilecommunications. W-CDMA evolved from GSM (Global System for MobileCommunications)/GPRS a second generation standard, which is oriented tovoice communications with limited data capability. The first commercialdeployments of W-CDMA are based on a version of the standards calledW-CDMA Release 99.

The Release 99 specification defines two techniques to enable Uplinkpacket data. Most commonly, data transmission is supported using eitherthe Dedicated Channel (DCH) or the Random Access Channel (RACH).However, the DCH is the primary channel for support of packet dataservices. Each remote station 123-127 uses an orthogonal variablespreading factor (OVSF) code. An OVSF code is an orthogonal code thatfacilitates uniquely identifying individual communication channels, aswill be appreciated by one skilled in the art. In addition, microdiversity is supported using soft handover and closed loop power controlis employed with the DCH.

Pseudorandom noise (PN) sequences are commonly used in CDMA systems forspreading transmitted data, including transmitted pilot signals. Thetime required to transmit a single value of the PN sequence is known asa chip, and the rate at which the chips vary is known as the chip rate.Inherent in the design of direct sequence CDMA systems is therequirement that a receiver aligns its PN sequences to those of the NodeB 110, 111, 114. Some systems, such as those defined by the W-CDMAstandard, differentiate base stations 110, 111, 114 using a unique PNcode for each, known as a primary scrambling code. The W-CDMA standarddefines two Gold code sequences for scrambling the downlink, one for thein-phase component (I) and another for the quadrature (Q). The I and QPN sequences together are broadcast throughout the cell without datamodulation. This broadcast is referred to as the common pilot channel(CPICH). The PN sequences generated are truncated to a length of 38,400chips. A period of 38,400 chips is referred to as a radio frame. Eachradio frame is divided into 15 equal sections referred to as slots.W-CDMA Node Bs 110, 111, 114 operate asynchronously in relation to eachother, so knowledge of the frame timing of one base station 110, 111,114 does not translate into knowledge of the frame timing of any otherNode B 110, 111, 114. In order to acquire this knowledge, W-CDMA systemsuse synchronization channels and a cell searching technique.

3GPP Release 5 and later supports High-Speed Downlink Packet Access(HSDPA). 3GPP Release 6 and later supports High-Speed Uplink PacketAccess (HSUPA). HSDPA and HSUPA are sets of channels and procedures thatenable high-speed packet data transmission on the downlink and uplink,respectively. Release 7 HSPA+ uses 3 enhancements to improve data rate.First, it introduced support for 2×2 MIMO on the downlink. With MIMO,the peak data rate supported on the downlink is 28 Mbps. Second, higherorder modulation is introduced on the downlink. The use of 64 QAM on thedownlink allows peak data rates of 21 Mbps. Third, higher ordermodulation is introduced on the uplink. The use of 16 QAM on the uplinkallows peak data rates of 11 Mbps.

In HSUPA, the Node B 110, 111, 114 allows several user equipment devices123-127 to transmit at a certain power level at the same time. Thesegrants are assigned to users by using a fast scheduling algorithm thatallocates the resources on a short-term basis (every tens of ms). Therapid scheduling of HSUPA is well suited to the bursty nature of packetdata. During periods of high activity, a user may get a largerpercentage of the available resources, while getting little or nobandwidth during periods of low activity.

In 3GPP Release 5 HSDPA, a base transceiver station 110, 111, 114 of anaccess network sends downlink payload data to user equipment devices123-127 on High Speed Downlink Shared Channel (HS-DSCH), and the controlinformation associated with the downlink data on High Speed SharedControl Channel (HS-SCCH). There are 256 Orthogonal Variable SpreadingFactor (OVSF or Walsh) codes used for data transmission. In HSDPAsystems, these codes are partitioned into release 1999 (legacy system)codes that are typically used for cellular telephony (voice), and HSDPAcodes that are used for data services. For each transmission timeinterval (TTI), the dedicated control information sent to anHSDPA-enabled user equipment device 123-127 indicates to the devicewhich codes within the code space will be used to send downlink payloaddata to the device, and the modulation that will be used fortransmission of the downlink payload data.

With HSDPA operation, downlink transmissions to the user equipmentdevices 123-127 may be scheduled for different transmission timeintervals using the 15 available HSDPA OVSF codes. For a given TTI, eachuser equipment device 123-127 may be using one or more of the 15 HSDPAcodes, depending on the downlink bandwidth allocated to the deviceduring the TTI. As has already been mentioned, for each TTI the controlinformation indicates to the user equipment device 123-127 which codeswithin the code space will be used to send downlink payload data (dataother than control data of the radio network) to the device, and themodulation that will be used for transmission of the downlink payloaddata.

In a MIMO system, there are N (# of transmitter antennas) by M (# ofreceiver antennas) signal paths from the transmit and the receiveantennas, and the signals on these paths are not identical. MIMO createsmultiple data transmission pipes. The pipes are orthogonal in thespace-time domain. The number of pipes equals the rank of the system.Since these pipes are orthogonal in the space-time domain, they createlittle interference with each other. The data pipes are realized withproper digital signal processing by properly combining signals on theN×M paths. It is noted that a transmission pipe does not correspond toan antenna transmission chain or any one particular transmission path.

Communication systems may use a single carrier frequency or multiplecarrier frequencies. Each link may incorporate a different number ofcarrier frequencies. Furthermore, an access terminal 123-127 may be anydata device that communicates through a wireless channel or through awired channel, for example using fiber optic or coaxial cables. Anaccess terminal 123-127 may be any of a number of types of devicesincluding but not limited to PC card, compact flash, external orinternal modem, or wireless or wireline phone. The access terminal123-127 is also known as user equipment (UE), a remote station, a mobilestation or a subscriber station. Also, the UE 123-127 may be mobile orstationary.

User equipment 123-127 that has established an active traffic channelconnection with one or more Node Bs 110, 111, 114 is called active userequipment 123-127, and is said to be in a traffic state. User equipment123-127 that is in the process of establishing an active traffic channelconnection with one or more Node Bs 110, 111, 114 is said to be in aconnection setup state. User equipment 123-127 may be any data devicethat communicates through a wireless channel or through a wired channel,for example using fiber optic or coaxial cables. The communication linkthrough which the user equipment 123-127 sends signals to the Node B110, 111, 114 is called an uplink. The communication link through whicha NodeB 110, 111, 114 sends signals to a user equipment 123-127 iscalled a downlink.

FIG. 11C is detailed herein below, wherein specifically, a Node B 110,111, 114 and radio network controller 141-144 interface with a packetnetwork interface 146. (Note in FIG. 11C, only one Node B 110, 111, 114is shown for simplicity.) The Node B 110, 111, 114 and radio networkcontroller 141-144 may be part of a radio network server (RNS) 66, shownin FIG. 11A and in FIG. 11C as a dotted line surrounding one or moreNode Bs 110, 111, 114 and the radio network controller 141-144. Theassociated quantity of data to be transmitted is retrieved from a dataqueue 172 in the Node B 110, 111, 114 and provided to the channelelement 168 for transmission to the user equipment 123-127 (not shown inFIG. 11C) associated with the data queue 172.

Radio network controller 141-144 interfaces with a Public SwitchedTelephone Network (PSTN) 148 through a mobile switching center 151, 152.Also, radio network controller 141-144 interfaces with Node Bs 110, 111,114 in the communication system 100B. In addition, radio networkcontroller 141-144 interfaces with a Packet Network Interface 146. Radionetwork controller 141-144 coordinates the communication between userequipment 123-127 in the communication system and other users connectedto a packet network interface 146 and PSTN 148. PSTN 148 interfaces withusers through a standard telephone network (not shown in FIG. 11C).

Radio network controller 141-144 contains many selector elements 136,although only one is shown in FIG. 11C for simplicity. Each selectorelement 136 is assigned to control communication between one or moreNode B's 110, 111, 114 and one remote station 123-127 (not shown). Ifselector element 136 has not been assigned to a given user equipment123-127, call control processor 140 is informed of the need to page theuser equipment 123-127. Call control processor 140 then directs Node B110, 111, 114 to page the user equipment 123-127.

Data source 122 contains a quantity of data, which is to be transmittedto a given user equipment 123-127. Data source 122 provides the data topacket network interface 146. Packet network interface 146 receives thedata and routes the data to the selector element 136. Selector element136 then transmits the data to Node B 110, 111, 114 in communicationwith the target user equipment 123-127. In the exemplary embodiment,each Node B 110, 111, 114 maintains a data queue 172, which stores thedata to be transmitted to the user equipment 123-127.

For each data packet, channel element 168 inserts the control fields. Inthe exemplary embodiment, channel element 168 performs a cyclicredundancy check, CRC, encoding of the data packet and control fieldsand inserts a set of code tail bits. The data packet, control fields,CRC parity bits, and code tail bits comprise a formatted packet. In theexemplary embodiment, channel element 168 then encodes the formattedpacket and interleaves (or reorders) the symbols within the encodedpacket. In the exemplary embodiment, the interleaved packet is coveredwith a Walsh code, and spread with the short PNI and PNQ codes. Thespread data is provided to RF unit 170 which quadrature modulates,filters, and amplifies the signal. The downlink signal is transmittedover the air through an antenna to the downlink.

At the user equipment 123-127, the downlink signal is received by anantenna and routed to a receiver. The receiver filters, amplifies,quadrature demodulates, and quantizes the signal. The digitized signalis provided to a demodulator where it is despread with the short PNI andPNQ codes and decovered with the Walsh cover. The demodulated data isprovided to a decoder which performs the inverse of the signalprocessing functions done at Node B 110, 111, 114, specifically thede-interleaving, decoding, and CRC check functions. The decoded data isprovided to a data sink.

FIG. 11D illustrates an embodiment of a user equipment (UE) 123-127 inwhich the UE 123-127 includes transmit circuitry 164 (including PA 108),receive circuitry 109, power controller 107, decode processor 158,processing unit 103, and memory 116.

The processing unit 103 controls operation of the UE 123-127. Theprocessing unit 103 may also be referred to as a CPU. Memory 116, whichmay include both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processing unit 103. A portion ofthe memory 116 may also include non-volatile random access memory(NVRAM).

The UE 123-127, which may be embodied in a wireless communication devicesuch as a cellular telephone, may also include a housing that contains atransmit circuitry 164 and a receive circuitry 109 to allow transmissionand reception of data, such as audio communications, between the UE123-127 and a remote location. The transmit circuitry 164 and receivecircuitry 109 may be coupled to an antenna 118.

The various components of the UE 123-127 are coupled together by a bussystem 130 which may include a power bus, a control signal bus, and astatus signal bus in addition to a data bus. However, for the sake ofclarity, the various busses are illustrated in FIG. 11D as the bussystem 130. The UE 123-127 may also include a processing unit 103 foruse in processing signals. Also shown are a power controller 107, adecode processor 158, and a power amplifier 108.

The steps of the methods discussed may also be stored as instructions inthe form of software or firmware 43 located in memory 161 in the Node B110, 111, 114, as shown in FIG. 11C. These instructions may be executedby the control unit 162 of the Node B 110, 111, 114 in FIG. 11C.Alternatively, or in conjunction, the steps of the methods discussed maybe stored as instructions in the form of software or firmware 42 locatedin memory 116 in the UE 123-127. These instructions may be executed bythe processing unit 103 of the UE 123-127 in FIG. 11D.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the exemplary embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the exemplary embodiments of the invention.

The various illustrative logical blocks, modules, and circuits describedin connection with the exemplary embodiments disclosed herein may beimplemented or performed with a general purpose processor, a DigitalSignal Processor (DSP), an Application Specific Integrated Circuit(ASIC), a Field Programmable Gate Array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theexemplary embodiments disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module may reside in Random AccessMemory (RAM), flash memory, Read Only Memory (ROM), ElectricallyProgrammable ROM (EPROM), Electrically Erasable Programmable ROM(EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any otherform of storage medium known in the art. An exemplary storage medium iscoupled to the processor such that the processor can read informationfrom, and write information to, the storage medium. In the alternative,the storage medium may be integral to the processor. The processor andthe storage medium may reside in an ASIC. The ASIC may reside in a userterminal. In the alternative, the processor and the storage medium mayreside as discrete components in a user terminal.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosed exemplary embodiments isprovided to enable any person skilled in the art to make or use thepresent invention. Various modifications to these exemplary embodimentswill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other exemplary embodimentswithout departing from the spirit or scope of the invention. Thus, thepresent invention is not intended to be limited to the exemplaryembodiments shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

1. A method comprising: receiving (510) symbols corresponding to acomposite channel during a first allotted transmission time interval(TTI), the composite channel comprising at least two multiplexedtransport channels; attempting (540.1) to decode at least one transportchannel prior to receiving all symbols of the first TTI; andtransmitting (560.1) an acknowledgement message (ACK) based on asuccessful decode, wherein the ACK is operable to cease transmission ofthe symbols during the first TTI.
 2. The method of claim 1, furthercomprising receiving symbols corresponding to the composite channelduring a second TTI following the first TTI.
 3. The method of claim 1,the attempting comprising attempting to decode at least two transportchannels prior to receiving all symbols of the first TTI.
 4. The methodof claim 3, the at least two transport channels comprising a first and asecond transport channel, the attempting to decode comprising attemptingto decode the second transport channel a predetermined time intervalafter attempting to decode the first transport channel.
 5. The method ofclaim 3, the attempting to decode comprising simultaneously attemptingto decode at least two transport channels.
 6. The method of claim 1,each TTI further sub-divided into slots, the attempting to decodecomprising attempting to decode once every fixed number of slots.
 7. Themethod of claim 1, the transmitting the ACK comprising multiplexing theACK transmission with a pilot transmission.
 8. The method of claim 7,the multiplexing the ACK transmission comprising multiplexing in time.9. The method of claim 7, the multiplexing the ACK transmissioncomprising multiplexing in code.
 10. The method of claim 1, the at leasttwo transport channels comprising at least two transport channels forcarrying AMR class A, B, and C bits.
 11. The method of claim 10, themethod further comprising decoding data for at least one of thetransport channels using a tail-biting convolutional code decoder. 12.The method of claim 1, the transmitting comprising transmitting on adownlink of a W-CDMA system, the receiving comprising receiving on anuplink of the W-CDMA system.
 13. The method of claim 1, the transmittingcomprising transmitting on an uplink of a W-CDMA system, the receivingcomprising receiving on a downlink of the W-CDMA system.
 14. The methodof claim 1, further comprising: receiving symbols corresponding tocomposite channels from at least two user equipments (UE's), theattempting to decode comprising prioritizing decoding attempts for theat least two UE based on whether a UE is in soft hand-off.
 15. Anapparatus comprising: a receiver (250) configured to receive symbolscorresponding to a composite channel during a first allottedtransmission time interval (TTI), the composite channel comprising atleast two multiplexed transport channels; a decoder (270) configured toattempt to decode at least one transport channel prior to receiving allsymbols of the first TTI; and a transmitter (430) configured to transmitan acknowledgement message (ACK) based on a successful result of thedecoding, wherein the ACK is operable to cease transmission of thesymbols during the first TTI.
 16. The apparatus of claim 15, thereceiver further configured to receive symbols corresponding to thecomposite channel during a second TTI following the first TTI.
 17. Theapparatus of claim 15, the decoder configured to attempt to decode atleast two transport channels prior to receiving all symbols of the firstTTI.
 18. The apparatus of claim 17, the at least two transport channelscomprising a first and a second transport channel, the decoderconfigured to attempt to decode the second transport channel apredetermined time interval after attempting to decode the firsttransport channel.
 19. The apparatus of claim 17, the decoder configuredto simultaneously attempt to decode at least two transport channels. 20.The apparatus of claim 15, each TTI further sub-divided into slots, thedecoder configured to attempt to decode once every fixed number ofslots.
 21. The apparatus of claim 15, the transmitter configured tomultiplex the ACK transmission with a pilot transmission.
 22. Theapparatus of claim 21, the transmitter configured to multiplex the ACKtransmission with the pilot transmission in time.
 23. The apparatus ofclaim 21, the transmitter configured to multiplex the ACK transmissionin code.
 24. The apparatus of claim 15, the at least two transportchannels comprising at least two transport channels for carrying AMRclass A, B, and C bits.
 25. The apparatus of claim 24, the decodercomprising a tail-biting convolutional code decoder.
 26. The apparatusof claim 15, the transmitter configured to transmit on a downlink of aW-CDMA system, the receiver configured to receive on an uplink of theW-CDMA system.
 27. The apparatus of claim 15, the transmitter configuredto transmit on an uplink of a W-CDMA system, the receiver configured toreceive on a downlink of the W-CDMA system.
 28. The apparatus of claim26, the receiver further configured to receive symbols corresponding tocomposite channels from at least two user equipments (UE's), theattempting to decode comprising prioritizing decoding attempts for theat least two UE based on whether a UE is in soft hand-off.
 29. Anapparatus comprising: means for receiving (510) symbols corresponding toa composite channel during a first allotted transmission time interval(TTI), the composite channel comprising at least two multiplexedtransport channels; means for attempting (540.1) to decode at least onetransport channel prior to receiving all symbols of the first TTI; andmeans for transmitting (560.1) an acknowledgement message (ACK) based ona successful decode, wherein the ACK is operable to cease transmissionof the symbols during the first TTI.
 30. The apparatus of claim 29, theat least two transport channels comprising at least two transportchannels for carrying AMR class A, B, and C bits.
 31. Acomputer-readable storage medium storing instructions for causing acomputer to: receive (510) symbols corresponding to a composite channelduring a first allotted transmission time interval (TTI), the compositechannel comprising at least two multiplexed transport channels; attempt(540.1) to decode at least one transport channel prior to receiving allsymbols of the first TTI; and transmit (560.1) an acknowledgementmessage (ACK) based on a successful decode, wherein the ACK is operableto cease transmission of the symbols during the first TTI.